Define "too high in carbs".... Cats don't *need* carbs, but they can use them. I'm pretty sure that unless I feed a homemade or raw diet, there's going to be a significant percentage of carbs in the food I feed to my cats.
I found a calculator which you input the nutritional analysis of a cat food and it spits out the actual carb percentage - carbs are bad for diabetic cats. http://www.scheyderweb.com/cats/catfood.html
When I put in the info from the Wellness Indoor, it came up with 31.1% carbs.
Their current food came in at 20.6%. So yeah, logically, there's more carbs in the Wellness comparatively, but I'm not sure that you can compare it just based on percentage - not all carbs are digested or absorbed in the digestive system, specifically comparings things like fibre to a starch. Both are considered carbs, but fibre doesn't get absorbed, it simply adds bulk and "roughage" to the diet. And the Wellness Indoor has 5% fibre while the EP Holistic has only 2.8%. There are other minerals which add to the carb total which aren't necessarily digested or absorbed in the same way, as well, including minerals and vitamins. They don't all add to fat, many are essential; not to mention that in comparing these two foods, they don't even list the same nutritional components, so I am comparing apples to oranges.

I have yet to find any real information backing up your claim that carbs cause alkaline urine, and in fact I found a source that says that a treatment for cats with crystals is actually a LOW-protein food (Veterinary advice from John Burns BVMS MRCVS). I did find lots of information that suggests what you are saying, but none of them are veterinary, and most refer to dogs - cats have a different physiology and react differently to many things in the enviroment.
That being said, the crystal "problem" is under control with the cranberry, which is a recommendation of my veterinarian.

I can't use Innova Evo - as I've said before, high protein foods trigger immediate bloody diarrhea in Taz. I expect that CORE, with it's exact same protein percentage as Evo would cause the same result. Not one I'm willing to try.

I appreciate that many of you think canned food is better for many reasons. It simply does not work in my house hold, for a variety of reasons, and it's not an option I'm willing to discuss further.

I have looked at the ingredients/nutritional analysis of their current food and the Wellness Indoor, and am willing to at least give it a try. The other Wellness formulas have similar analysis and I really don't think there's a significant difference between them.